Add the interval between mining blocks

In the server, it is often too fast to dig the block, and it needs to be dug too many times to dig it out. If you can add a code to set the interval between digging one block each time and digging the next block for a period of time, it will not get stuck

No files, tests, or entry points are named. Start by locating the server-side block-mining logic and trace how one block is followed by the next; done means a configurable interval can be applied between mining attempts without the process getting stuck.

Written by the indexing model from the issue text.